Interleukin-1 Receptor Antagonism Abrogates Acute Pressure Overload-Induced Murine Heart Failure.

BACKGROUND: Recent clinical trials have suggested that blockade of interleukin-1 (IL-1) can have a favorable impact on patients with myocardial infarction and heart failure. However, the mechanism of antagonism of this specific cytokine in mediating cardiac disease remains unclear. Hence, we sought to determine the influence of IL-1 blockade on acute hypertensive remodeling. METHODS: Transverse aortic constriction was performed in C57BL mice with or without intraperitoneal administration of interleukin 1 receptor antagonism (IL-1Ra). Function, structure, and molecular diagnostics were subsequently performed and analyzed. RESULTS: Six weeks after transverse aortic constriction, a progressive decline of ejection fraction and increases in left ventricle mass and dimensions were effectively mitigated with IL-1Ra. Transverse aortic constriction resulted in an expected profile of hypertrophic markers including myosin heavy chain, atrial natriuretic peptide, and skeletal muscle actin, which were all significantly lower in IL-1Ra treated mice. Although trichrome staining 2 weeks after transverse aortic constriction demonstrated similar levels of fibrosis, IL-1ra-reduced expression of collagen-1, tissue inhibitor of metallopeptidase 1, and periostin. Investigating the angiogenic response to pressure overload, similar levels of vascular endothelial growth factor were observed, but IL-1Ra was associated with more stromal cell-derived factor-1. Immune cell infiltration (macrophages and lymphocytes) was also decreased in IL-1Ra treated mice. Similarly, cytokine concentrations of IL-1, IL-18, and IL-6 were all reduced in IL-1Ra-treated animals. CONCLUSIONS: Interleukin-1Ra prevents the progression toward heart failure associated with acute pressure overload. This functional response was associated with reductions in mediators of fibrosis, cellular infiltration, and cytokine production. These results provide mechanistic insight into recent clinical trials and could springboard future investigations in patients with pressure-overload-based cardiomyopathies.

Cardiomyocyte p65 nuclear factor-κB is necessary for compensatory adaptation to pressure overload.

BACKGROUND: Nuclear factor κB (NF-κB) is often implicated in contributing to the detrimental effects of cardiac injury. This ostensibly negative view of NF-κB competes with its important role in the normal host inflammatory and immune response. We have previously demonstrated that pharmacological inhibition of NF-κB at the time of acute pressure overload accelerates the progression of left ventricular hypertrophy to heart failure in mice. NF-κB regulates angiogenesis and other factors responsible for compensatory reaction to intracellular hypoxia. We hypothesized that impaired angiogenesis may be the trigger, not the result, of pathological left ventricular hypertrophy through NF-κB-related pathways. METHODS AND RESULTS: Transgenic mice were generated with cardiomyocyte-specific deletion of the p65 subunit of NF-κB. Mice underwent transverse aortic constriction and serially followed up with echocardiography for 6 weeks. Cardiomyocyte p65 NF-κB deletion promoted maladaptive left ventricular hypertrophy and accelerated progression toward heart failure as measured by ejection fraction, left ventricular mass, and lung congestion. Transgenic mice had higher levels of fibrosis and periostin expression. Whole-field digital microscopy revealed increased capillary domain areas in knockout mice while concurrently demonstrating decreased microvessel density. This observation was associated with decreased expression of hypoxia-inducible factor 1α. CONCLUSIONS: Rather than developing compensatory left ventricular hypertrophy, pressure overload in cardiomyocyte NF-κB-deficient mice resulted in functional deterioration that was associated with increased fibrosis, decreased hypoxia-inducible factor expression, and decreased microvessel density. These observations mechanistically implicate NF-κB, and its regulation of hypoxic stress, as an important factor determining the path between adaptive hypertrophy and maladaptive heart failure.

Animal model of reversible, right ventricular failure.

BACKGROUND: Heart failure is a leading cause of death but very little is known about right ventricular (RV) failure (RVF) and right ventricular recovery (RVR). A robust animal model of reversible, RVF does not exist, which currently limits research opportunities and clinical progress. We sought to develop an animal model of reversible, pressure-overload RVF to study RVF and RVR. MATERIALS AND METHODS: Fifteen New Zealand rabbits underwent implantation of a fully implantable, adjustable, pulmonary artery band. Animals were assigned to the control, RVF, and RVR groups (n = 5 for each). For the RVF and RVR groups, the pulmonary artery bands were serially tightened to create RVF and released for RVR. Echocardiographic, cardiac magnetic resonance imaging, and histologic analysis were performed. RESULTS: RV chamber size and wall thickness increased during RVF and regressed during RVR. RV volumes were 1023 µL ± 123 for control, 2381 µL ± 637 for RVF, and 635 µL ± 549 for RVR, and RV wall thicknesses were 0.98 mm ± 0.12 for controls (P = 0.05), 1.72 mm ± 0.60 for RVF, and 1.16 mm ± 0.03 for RVR animals (P = 0.04), respectively. Similarly, heart weight, liver weight, cardiomyocyte size, and the degree of cardiac and hepatic fibrosis increased with RVF and decreased during RVR. CONCLUSIONS: We report an animal model of chronic, reversible, pressure-overload RVF to study RVF and RVR. This model will be used for preclinical studies that improve our understanding of the mechanisms of RVF and that develop and test RV protective and RVR strategies to be studied later in humans.